Press Articles
The Liphook Build
Read the article in Build It.The young couple, who are the subject of the Build It article, had stumbled across a building plot for sale by private treaty when searching for a house. They had absolutely no building experience and were rather daunted by all the processes involved before the build could start, let alone the building process itself. Fortunately their nerve held and they now have a highly efficient home that they just could not buy from a developer, as it far exceeds the performance required by regulations and at a much lower finished cost.
The developer was the second to own the site and it had been the subject of 9 failed planning applications (mostly on the grounds of objections by neighbours and proposed density).
The plot was sold with planning for a single, detached dwelling of 100 sq m and single, detached garage. The developer undertook to lay in the utilities to a position adjacent to the plot, construct the road (which was to become private and not adopted by the council) and landscape the areas to the side of the road.
Avilion Sustainable Homes Limited project managed the build in a flexible way to allow the couple to complete what tasks they, or their family could.
First Task was to apply for an extended building. Having reviewed the planning history, it became obvious that no change to the front elevation or to the ridge height would be viewed favourably by planners. The couple had no great desire for additional, or larger bedrooms but the dining room of the original plan was cramped, to say the least.
A new rear and side elevations were drawn and discussed with planners, who raised no objection and who used their delegated powers to pass the plans without undue delay.
Second task involved preparing full building regulation drawings, after detailed discussion with the client as to what levels of insulation and energy consumption they were trying to achieve.
The specification was arrived at having decided performance to Code 3 of the code for sustainable homes was a desirable target and achievable within the budget.
A 140mm, timber frame was selected as the basis of the construction but with its performance enhanced by the use of a reflective vapour membrane and service void, combined with a breather membrane (U Foil VBF) and external, 50mm cavity. This pushed the U value from 0.27 W/m2K to 0.20 W/m2K with no increase in wall thickness (other than the 25mm services void which eased first fix of electricity and plumbing and assisted in obtaining an excellent air leakage test result). The frame was insulated with 140mm of Rockwool Flexi TM.
The low ridge height of 6.5m meant all the upstairs rooms were in the roof space with low, knee walls of just over 1 metre. Insulation values close to Passivhaus were achieved. The couple wished to fix the insulation themselves and 200mm of Rockwool Flexi was placed between the rafters, held in place by a polythene vapour barrier. While making the building watertight, immediately after frame erection, we fitted a layer of Gen-XTM, foil insulation over the rafters and held in place by the tile counter battens. This gave a resultant U value of 0.15 W/m2K (c.f. Passivhaus 0.13 W/m2K). Given the great percentage of the upstairs volume enclosed by this level of insulation, this has resulted in a very efficient building. In fact, the owners have not felt it necessary to turn on their radiators at all, having now been in residence in two winters.
Avilion contracted timber frame supply and erection, foundations, brickworks, roofing, first and second fix electrical works and supply and fixing of the solar hot water panel. We supplied and fitted the under floor heating and had it screeded with liquid, anhydrite screed. This screed is fast, exceptionally level, dries faster than sand and cement and maintains intimate contact with the pipes, while only being required to be 50mm thick (c.f. 65mm for sand and cement). This has a significant effect on the responsiveness and hence running costs, of the heating system.
The couple called on family members to fix the insulation, fix the Fermacell wall board (a superior wall board with high strength that permits cabinets to be fixed directly to it by simple screwing and which has better sound transmission qualities than similar thickness plasterboard) and plasterboard to the ceilings but plasterers were called when tacking out was complete.
Family members also tiled and decorated, fitted skirting and architraves, flooring and the kitchen. They contracted the landscaping work.
Our involvement was also required when building control took issue with a wood burning stove having no external vent. There should have been no issue. The regulations state quite clearly that a fire of 5Kw, or less, needs no vent. A Villavent, heat recovery and ventilation unit was fitted and measured to be delivering 47 cu m of air per hour into the living room. The building control officer had the full plans submission that showed the fire, the heat recovery unit and no vent but dug his heels in on final inspection of the building. Not only would a vent compromise the very concept of a heat recovery unit, it would have destroyed the air tightness that was achieving a rating very close to code 4 (target was code 3). All this fuss for a fire that can only hold sufficient logs to burn for 2 hours at the most, if completely shut down. The fire had been installed by a HETAS engineer (as required by regulations), who had approved the installation as safe. The couple were the victims of officialdom gone mad. Fortunately we were able to provide calculations that demonstrated the fire would burn out long before it consumed the available oxygen and that the Villavent unit, even in a power failure, would permit sufficient air past its fan to supply the fire.
Our advice to anyone contemplating fitting a wood burner, in conjunction with heat recovery and ventilation, would be to install a balanced flue (room sealed) fire and not open chimney. Where building regulations conflict, as in this case, try to take away any ambiguity.
The total energy costs for this house were calculated at £395 for the entire year. In fact, the owners had no need to use supplementary heating for hot water all summer and the solar gain is minimising the need for under floor heating as well.